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With the rapid development of high-frequency wireless communication technologies, the FR3 frequency band (7.125–8.5 GHz) has gradually become an important spectrum for next-generation communication and radar systems due to its abundant bandwidth and relatively low interference. This project aims to implement an integrated RF front-end module that includes a low-noise amplifier (LNA), power amplifier (PA), and a Yagi array antenna, in order to enhance the overall communication performance and system stability. In the circuit design, both the LNA and PA adopt a common-emitter configuration with emitter inductive negative feedback to improve circuit stability. The LNA utilizes the Infineon BFP720F transistor and incorporates a fifth-order hairpin bandpass filter to enhance frequency selectivity. The PA employs the BFP760 transistor, together with a two-stage Π-type matching network, a diode limiter, and a low-pass filter to improve linearity and suppress harmonic components. For the antenna design, a 1 × 4 Yagi dipole array is adopted and integrated with a Wilkinson power divider for the feeding network, thereby improving antenna directivity and gain. According to the link budget estimation, under the conditions of a PA output power of 18.2 dBm, LNA gain of 18 dB, antenna gain of 11.5 dBi, and system loss of 3 dB, the maximum communication distance can reach 185 m at 7.8 GHz with an SNR of 20 dB using 64-QAM modulation. If QPSK modulation is employed, the communication distance can be extended to 561 m.

With the rapid development of 5G communication technology, the large-scale deployment of 5G small cell antennas has become an inevitable trend in mobile communication network infrastructure. This project focuses on the design and implementation of a compact dual-polarized base station antenna for the 5G NR n77 band. The research is divided into two main parts: single-antenna design and antenna array design.
In the single-antenna design, a crossed dipole structure is adopted as the antenna architecture to achieve ±45° dual-polarization characteristics. The overall antenna design emphasizes miniaturization. The three-dimensional antenna structure has dimensions of 50 × 50 × 24.6 mm³, while the planar antenna size is only 20.1 × 20.1 mm², making it suitable for various indoor small-cell deployment scenarios. The antenna substrate is designed and simulated using an FR4 fiberglass printed circuit board with a thickness of 0.8 mm. Through multiple structural optimization techniques, the antenna maintains good performance while achieving compact size.

Simulation results show that within the operating frequency band, the reflection coefficient (S11) is less than −10 dB, the isolation (S21) is lower than −20 dB, and the antenna efficiency exceeds 90%.
To further enhance the antenna gain, an antenna array design is also investigated in this study, adopting a 2 × 2 array configuration. Simulation results indicate that within the operating band, the reflection coefficient (S11) is below −10 dB, the isolation (S21) is below −15 dB, and the peak gain can reach 12 dBi.
In terms of practical fabrication and measurement, the experimental results show good agreement with the simulation results, thereby verifying the feasibility and effectiveness of the proposed antenna design.